An overwhelming majority of Ireland's electorate will back the introduction of gay marriage in the one-time Catholic Church dominated Republic.

A new opinion poll shows that only just under 20% of voters will oppose introducing same sex marriage into the Irish constitution.

More than three-quarters of voters say they support marriage equality for lesbian, gay, bisexual and transgender (LGBT) people in a proposed referendum by the Fine Gael-Labour coalition.

The survey by the Red C opinion poll firm for Irish public broadcaster RTÉ and The Sunday Business Post found that 76% would be in favour of allowing LGBT couples to legally marry in the Irish Republic. Around 5% of voters were undecided and 19% opposed the law reform.

The poll was published in the same week that BBC TV chat show host Graham Norton intervened in what has been a controversial and heated media debate in Ireland.

Norton predicted his fellow Irish citizens would support gay marriage equality in the referendum when it is called before the next general election.

The County Cork born presenter said the Republic was a very different place from when he was growing up.

"When I go back now – and I pretty much spend my entire summer near to where I grew up in Bandon – it's such a different place. It takes pride in accepting all types of people. There's more than 40 shades of green," Norton told the current edition of the Irish music magazine Hot Press.

Norton also used the interview to launch a stinging attack on RTÉ for paying up to €80,000 (£66,000) in libel costs to a number of Irish media commentators who had been accused of being homophobic. In at least one case one of these writers, the columnist John Waters, later stated he had never sought libel damages from the broadcaster. He branded the libel payout as "moronic".

The TV talk show host also praised the current "star" of the gay marriage debate in Ireland, a drag queen and gay bar owner known as Miss Panti.

AKA Rory O'Neill, Panti won global praise for a speech he made at Dublin's Abbey Theatre last month in which he detailed how he had been the target of homophobic abuse in Ireland. Miss Panti's public recounting of homophopic attacks gained the support of Madonna and Stephen Fry among others on the Twittersphere.

"It's a very sane speech, which exists outside of the current argument," Norton told the Irish music magazine.

"You don't need to know about all the RTÉ to-ings and fro-ings to understand it. Rory's a smart chap and it was perfectly pitched."